How to switch between different models?

How can I switch between two models with different behaviors while still using the same character when a key is pressed?

Or if needs to be two different characters how to make the other one disappear while the one in use appears and vice versa? This is for a 2D game.

If you want to simply change the skeletal mesh used by your character, access the SkeletalMeshComponent of your character and assign a new Skeletal mesh to it.